Impact protection enclosure for a mobile electronic device

ABSTRACT

An add-on protective housing to improve protection of a portable electronic device. Certain embodiments include a hard external shell in the general conformation of the electronic device. The hard shell includes one or more aperture through which one or more control of the contained device may be operated. An energy distributing layer is disposed between the electronic device and the inner surface of the hard shell to space the device apart from the shell. Certain embodiments may provide fluid and/or dust resistance to the contained device.

BACKGROUND OF THE INVENTION

1. The Field of the Invention

The present invention relates to impact-protecting add-on devices. In particular, a preferred embodiment forms an add-on enclosure to increase protection for a selected mobile electronic device from at least impact.

2. Related Art

Portable electronic devices are becoming smaller, more sensitive, and costly to replace, yet the current standard for protection is believed to be inadequate. Exemplary such electronic devices includes cell-phones. There are many commercially available housings structured to provide add-on protection for certain of such electronic devices, yet none have sufficiently addressed the need for impact protection.

Most protective cases for mobile electronic devices have been introduced in the form of scratch- and mar-resistant, add-on enclosures, with an emphasis on color, style or fashion. Many protective cases are designed to add a minimal amount of impact protection in the form of a stretch-to-fit silicone skin, which leaves the device most vulnerable to impact on the corners and edges of the device. Even fewer protective cases are designed to add impact, or drop protection as a main goal of the design. Examples of such protective cases are disclosed in U.S. Pat. No. 7,933,122 and US patent application 2010/0147737. Even the add-on cases disclosed in the aforementioned documents, and designed for impact protection, leave room for further improvement.

BRIEF SUMMARY

The invention may be embodied to provide an add-on enclosure to increase ruggedness of a commercially available portable electronic device. A preferred enclosure includes a hard shell configured in general agreement with the exterior of the electronic device. A workable enclosure includes six sides, including a front side, back side, top side, bottom side, left side, and right side. The sides generally define a first volume. One or more window is disposed in one or more of the sides to permit operation of at least one control of the electronic device when the electronic device is contained inside the shell. Preferred embodiments also include an energy distributing layer structured for disposition inside the shell and defining a second volume in which to receive the electronic device. Typically, the energy distributing layer is arranged to space a portion of the electronic device apart from direct contact with the shell.

A preferred hard shell includes a plurality of elements that may be assembled to form a uni-body enclosure. One such hard shell includes a tub and a cover. Uni-body enclosures can form very strong structures with efficient use of material. An exemplary hard shell structured according to certain principles of the invention is structured to contain a telephone and to carry a minimum 3-point load in excess of about 25 pounds, where the load is applied at the midpoint of a 4 inch span.

A preferred embodiment includes a cover, a top tub, and a bottom tub. A slide rail system of that embodiment is formed in combination between the cover, top tub, and bottom tub, and is configured to permit slide-assembly of each tub onto the cover. A detent-and-ramp structure is associated with such slide rail system, and is configured and arranged to resist sliding a tub from an installed position. Further, a push-button flex latch is carried by one tub and is configured and arranged to removably couple the top tub to the bottom tub when the tubs are in an assembled location on the cover. It is helpful to form a relief area in the energy distributing element to permit a user to impart a transverse deflection to the latch to permit separation of a tub from the cover.

A perimeter edge of a tub may includes a shelf and a cantilevered rim. One workable rim is adapted to overlap structure of a cooperating cover at a joint there-between. For example, a cantilevered flange can project from an inside surface of the cover and skirt a portion of the perimeter edge of the cover. The flange is advantageously arranged to overlap the rim at their mutual joint.

Sometimes, wall elements of a flange and a cooperating rim can carry retention structure, such as a plurality of cylinder-in-socket retention structures. Is such case, the retention structures are desirably configured to effect a snap-together connection between tub and cover to form a uni-body enclosure that can be assembled and disassembled a plurality of times without requiring destruction of retention structures. Desirably, the sides of a hard shell are structured and arranged in harmony with the energy distributing layer such that impact energy, generated by dropping the apparatus onto a flat surface, cannot be transferred to an electronic device contained inside the apparatus without first passing through the shell and a portion of the energy distributing layer.

A workable energy distributing layer comprises an elastomeric compound. An energy distributing layer can be formed from, or include, memory foam. The currently preferred energy distributing layer includes a two-pocket element, each such pocket being structured to engage a portion of an electronic device in direct contact therein. The two-pocket element is structured and arranged to be stretch-fit onto an electronic device during assembly of the protective enclosure. An energy distributing layer can include a first pocket configured to fit onto the top of an electronic device and a second pocket configured to fit onto the bottom of the electronic device. Such pockets may be discreet and separate elements. In general, an energy distributing layer can include a plurality of discrete sections of energy distributing material. Sometimes, a portion of an energy distributing layer is affixed to an inside surface of the hard shell.

Sometimes, a hard shell is structured in harmony with an energy distributing layer, an electronic device, and one or more membrane associated with one or more window, to permit placing the shell into a fluid-resistant configuration. In a preferred embodiment, a portion of an energy distributing layer is arranged as a door configured to cooperate with a first window in the hard shell to permit forming a dust-resistant seal there-between, a hinge of the door permitting rotation of the door in an outward direction through the first window. A membrane may sometimes be included to cover a second window in one of the sides of a hard shell to increase fluid and/or dust resistance. In certain cases, such a membrane is removable and replaceable. Certain embodiments may includes a gasket configured and arranged directly to form a water-resistant seal between a hard shell and enclosed electronic device. In one circumstance, a gasket is disposed around a perimeter of a display window of the hard shell such that a display window of the electronic device directly provides an area effective to resist fluid entry into the shell.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, which illustrate what are currently regarded as the best modes for carrying out the invention, and in which like structure is generally indicated with like numerals:

FIG. 1 is an exploded assembly view in perspective from the front of an assembly that is constructed according to certain principles of the instant invention

FIG. 2 is a front view in perspective illustrating assembly of certain elements of the embodiment of FIG. 1;

FIG. 3 is a view taken through section 3-3 in FIG. 2, and looking in the direction of the arrows;

FIG. 4 is a partial-assembly exploded view in perspective from the back;

FIGS. 4A-C are views of certain elements in FIG. 4, looking from the inside toward the exterior surface;

FIG. 5 is a view similar to that in FIG. 4, and illustrating a further step in assembly of the embodiment in FIG. 1;

FIG. 6 is a front view in perspective of the embodiment in FIG. 1 in a fully assembled configuration;

FIG. 7 is an exploded assembly view in perspective from the back of a shell element of the assembly of FIG. 1;

FIGS. 7A-C are close-up views of areas in FIG. 7 indicated respectively by balloons designated in accordance with FIG. designations;

FIG. 8 is an exploded assembly view in perspective from the front of the shell embodiment of FIG. 7;

FIGS. 8A-C are close-up views of areas in FIG. 8 indicated respectively by balloons designated in accordance with FIG. designations;

FIG. 9 is a view in perspective from the front of the shell embodiment of FIG. 7, partially in cross-section;

FIGS. 9A-B are close-up views of areas in FIG. 9 indicated respectively by balloons designated in accordance with FIG. designations;

FIG. 10 is a view in perspective from the back of the shell embodiment of FIG. 7, partially in cross-section;

FIGS. 10A-C are close-up views of areas in FIG. 10 indicated respectively by balloons designated in accordance with FIG. designations;

FIG. 11 is a top view of structure illustrated in FIG. 10B, as indicated by section 11-11 and looking in the direction of the arrows;

FIG. 12 is an exploded assembly view in perspective from the front of an alternative embodiment within the ambit of the instant invention;

FIG. 13 is an exploded assembly view in perspective from the front of an alternative embodiment within the ambit of the instant invention; and

FIG. 14 is an exploded assembly view in perspective from the front of an alternative embodiment within the ambit of the instant invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

The present invention provides an apparatus and method for increasing shock protection of a portable electronic device. A preferred embodiment forms an add-on external enclosure structured to increase ruggedness of a commercially available portable electronic device, such as a telephone.

As illustrated in FIG. 1, one embodiment of an enclosure structured according to certain principles of the invention is generally indicated at 100. Enclosure 100 includes a shell, generally 102, configured in general agreement with the exterior of a selected electronic device 104. A preferred shell 102 may be characterized as a hard shell. The illustrated electronic device 104 is a wireless telephone, but such is not intended to limit the scope of the instant invention. A wide variety of portable electronic devices having a variety of external configurations may benefit from improved shock resistance when used in combination with an embodiment structured according to certain principles of the instant invention. For purpose of this disclosure, electronic device 104 is intended to illustrate a generic element and to encompass portable electronic devices, generally.

Enclosure 100 includes a cover 106, and a tub, generally 108. Illustrated tub 108 includes a top tub 110, and a bottom tub 112. Enclosure 100 may be characterized as defining a volume 114 disposed inside of a front side 116, back side 118, top side 120, bottom side 122, left side 124, and right side 126. A side may sometimes be made reference to alternatively as a wall, or a shell, or shell element. It is recognized that there may be a grey area of distinction between exact boundaries of such sides, e.g. due to rounded corners, but for purpose of this disclosure, even a round ball has the six sides set forth above.

It is preferred to include one or more window, aperture, or opening disposed in one or more side to permit operation of at least one control of an electronic device 104 when the electronic device 104 is contained inside a protective enclosure, such as enclosure 100. As illustrated, enclosure 100 includes window 128 to permit access to a touch-screen; aperture 130 to permit operation of a push-button; one or more opening 132 for microphone pick-up; button operation openings 134 and 136; power access port 138; speaker and camera opening 140; camera apertures 142 and 144; main I/O aperture 146; and headphones access port 148. Other workable embodiments of an enclosure may have more, or fewer, access ports, apertures, openings, or windows, and the like.

With continued reference to FIG. 1, an energy distributing layer, or liner, generally 150, is structured for disposition inside of shell 102. Energy distribution layer 150 defines a second volume 152 in which to receive the electronic device 104. Second volume 152 is smaller than first volume 114. Preferably, energy distributing layer 150 is configured and arranged to space a portion of electronic device 104 apart from direct contact with the shell 102 of an assembly 100. In highly preferred embodiments, the soft liner 150 is disposed to cover at least 80% of the top, bottom, left, and right sides. Further, a highly preferred layer 150 covers at least 5% of the front side, and 50% of the back side of a device 104 contained therein. The highly preferred layer 150 is desirably distributed in some way over these surfaces.

It is currently most preferred that the layer 150 is configured to space the entirety of device 104 from contact to the shell 102, upon initial assembly. That is, it is desirable for the sides of a hard shell, such as shell 102, to be structured and arranged in harmony with an energy distributing layer 150 such that impact energy, generated by dropping the assembled device 100 onto a horizontal flat surface, cannot be transferred to an electronic device 104 contained inside hard shell 102 without first passing through a portion of the energy distributing layer 150. Of course, it is to be realized that, for purpose of the aforementioned test of dropping the device onto a flat surface, that flat surface necessarily is defined as a flat surface that is larger than can fit into a shell window or aperture, for example.

Still with reference to FIG. 1, energy distribution layer 150 permits user interaction with control elements of an electronic device, such as device 104, by way of openings, flaps, doors, flexible membranes, and the like, which are disposed in harmony with the access openings penetrating through sides of hard shell 102. In certain cases, such as the touch-screen access opening 128, a similar touch-screen access opening 128′ is provided in layer 150. When such openings in liner 150 are substantially similar to openings of the shell 102, they are typically assigned the same numerical designation in this disclosure, but also including a prime. For examples, the illustrated energy distributing layer 150 includes: power access port 138′; and camera apertures 142′ and 144′.

In other instances, the energy distributing layer 150 may include one or more intermediary movable structure, such as flexible link element 154, which is configured for displacement by a user to operate one or more push-button of a device 104. Flexible link element 156 performs a similar function. Desirably, the exemplary flexible link elements 154 and 156 are integral parts of the wall of the liner 150, and therefore inherently resist entry of water, dust, and the like, through respective apertures 146 and 130 for contact with the electronic device 104.

Flexible link element 158 is structured as a hinged door that can be opened by a user to permit access through opening 146 in shell 102. In the illustrated embodiment, a hinge is formed by an edge of the door 158 being integral with the wall of liner 150. The hinge of door 158 permits the door 158 to open outwardly, extending through the aperture 146. Desirably, door 158 is configured either in harmony with the aperture 146 or a local portion of the liner 150 (in a closed position) to form a resistant barrier to water, dust, and the like through aperture 146 for contact with a device 104.

A currently preferred energy distributing layer 150 is formed from, or includes, an elastomeric compound. A workable elastomeric compound includes silicone, rubber, and the like. An alternative operable energy distributing layer 150 may be formed from, or include a portion of, memory foam. In certain embodiments, a portion of a workable energy distributing layer 150 may be biased in compression upon assembly of a shell 102 to enclose a device 104 within a liner 150. In other circumstances, one or more air gap may be provided between a hard shell and the enclosed electronic device and/or a portion of an energy-distributing liner.

With reference now to FIG. 2, the illustrated energy distributing layer 150 is structured as a two-pocket element. A first pocket, generally 160, is disposed at the bottom end, generally 162, of the liner 150. A second pocket, generally 164, is disposed at the top end, generally 166, of the liner 150. Each pocket 160, 164 is structured to engage a portion of an electronic device 104 in direct contact therein. Pocket 160 receives the bottom end, generally 168, of device 104. Pocket 164 is configured to receive top end, generally 170, of device 104. The illustrated two-pocket layer 150 is structured and arranged to be elastically stretch-fit onto an electronic device 104 during assembly of a protection device 100. A device 104 can essentially be shoe-horned into seated engagement inside layer 150. During assembly, layer 150 is typically stretched to space the pockets 160, 164 apart, and lip 172 is pulled back to insert end 170 into reception inside pocket 164.

An alternative energy distributing layer 150 within contemplation includes a plurality of discrete sections of energy distributing material. For example, first and second pockets 160, 164 may be separate elements, unconnected by an elastic coupling element. (One such autonomous pocket is illustrated by the structure shown in FIG. 3). Strips, bands, or sections, of resilient energy-distributing material may be disposed to cover only selected areas of a device 104. One or more air space, or gap, may be provided between a device 104 and an internal surface of a hard shell, such as shell 102. In certain cases, a portion of an energy distributing layer may be affixed to an inside surface of a hard shell, such as shell 102.

With reference to FIG. 3, the wall of certain portions of layer 150, such as that forming part of pocket 160, may be shaped to provide desired functionality. In FIG. 3, it can be seen that button 156 is structured to provide a central presser-nub 172 and elastic bridge 174 of reduced thickness. Such structural arrangement facilitates resilient operation of button 156 to operate a control of device 104. (A similar arrangement is typically included in structure of flexible link element 154). Also, the internal side of door 158 includes ribs 176 spaced apart by areas of reduced thickness. Such arrangement maintains a more consistent thickness throughout, and facilitates molding an energy distributing layer 150 from material such as silicone.

FIG. 4 illustrates a device 104 installed in an energy distributing layer 150, and prepared for installation in registration with cover 106. A relief area 178 may sometimes be included in layer 150. An edge of door 180 is integral with the layer 150 to form a hinge 182. Similar to door 158, door 180 may be user-displaced through an aperture of the shell 102 to provide access to the device 104 to receive the probe portion of an electrical connector, such as for a pair of ear buds or a headset. Further, illustrated door 180 provides an access opening 184 through which to receive voice stimulus for a microphone collocated with an electrical connector of device 104. In certain cases, access opening 184 may be self-sealing to resist entrance of water and/or dust inside the layer 150.

Still with reference to FIG. 4, and similar to flexible link element 154, control actuator button 186 is illustrated as being integral around its periphery to resist entrance of water and/or dust inside the layer 150. As shown in FIG. 4A, the inside surface of a portion of layer 150, such as flexible link 154, may be configured in harmony with controls of a device 104. s illustrated, a pair of sockets 188 are provided in which to receive protruding control elements of device 104. As illustrated in FIG. 4C, a presser element 190 may be arranged similar to element 172 of button 156 (see FIG. 3).

Thickness, shock absorbing, dampening, cushioning, smooth distribution of point loads, load suspension, and energy dissipating capabilities or properties are important considerations and design trade-offs for an operable energy distributing layer 150. Beside silicone materials, foam which might have a durometer of as low as 20 may be used in certain embodiments. However, a silicone, or silicone-like, material having a Shore A durometer of between 40 and 90 is currently preferred for energy distributing layer 150. A currently preferred thickness for layer 150 is between about 0.01 and about 0.1 inches.

If the layer 150 is sufficiently compressible (e.g. foam having a Shore A value of about 20) layer 150 can be pre-loaded with a little compression (without worrying about resonance) which helps reduce overall layer thickness. If the durometer number is a little higher(say 40) a small air space between shell and layer 150 may be included, which gap acts as another suspension layer (and helps with assembly and manufacturing tolerances). The air gap bottoms out before the energy distributing layer engages with the hard shell, which can provide higher levels of protection like survivability from a higher drop. Also, the softness of a layer 150 is integral with the feel of the button and flex door features which also may drive the design depending on the size and placement of the device controls.

FIGS. 4-6 illustrate certain details of assembly of embodiment 100. As shown in FIG. 4, a device 104 installed in layer 150 is placed in registration inside cover 106. Slide rail structure, generally 194, of top tub 106 is engaged with corresponding slide rail structure, generally 196 of cover 106, and the tub 110 is slidingly displaced in an axial direction to cover the top end 166 of layer 150. Similarly, slide rail structure, generally 198, of bottom tub 112 is engaged with cooperating slide rail structure, generally 200, of cover 106, and tub 112 is slidingly displaced in an axial direction to cover bottom end 162 of layer 150. Either top tub 110, or bottom tub 112 may be installed first or second.

With particular reference to FIG. 5, during installation, push-button flex latch 202 is seated in engagement inside socket 204, and resists undesired separation of top tub 110 from bottom tub 112. Relief area 178 in layer 150 is desirably structured to provide clearance for transverse displacement of the push-button flex latch 202 during assembly and disassembly. Naturally, a workable latch and socket arrangement may be arranged in alternative configurations, e.g. with the illustrated latch and socket being carried by the other tub, or with a plurality of latches and sockets being carried between the two tubs 110, 112, for non-limiting examples.

As shown in FIG. 6, the assembled hard shell 102 desirably provides the visual appearance of an uninterrupted shell. That is, seams or separable joints, generally 206, between a cover 102 and one or more tub, such as tub 110 or tub 112, are desirably inconspicuous. A currently preferred hard shell 102 includes a plurality of separable elements that may be assembled to form a uni-body enclosure. A uni-body enclosure, as illustrated, may be characterized as having separable joints between constituent elements that include a frame surrounded by a frame effective to translate in-plane shear deformation to bending loads that are carried by constituent shell members, thereby forming a stiffer assembly to inherently resist twist or bending force that may be applied to the assembled hard shell. Desirably, separable joints of a hard shell are structured to provide self-reinforcement or mutual reinforcement against joint rotation at the joint area. Desirably a joint is structured such that impact forces tend to further close a portion of the joint.

FIGS. 7-10 illustrate details of construction of a currently preferred slide rail system, and in particular how a slide rail system is formed in combination between the cover 106, top tub 110, and bottom tub 112. With reference to FIG. 7A, slide rail structure 200 includes a rail 208 that is cantilevered from a perimeter of the cover 106. Rail 208 includes an elongate socket 210 and a lip 212. A detent 214 is disposed to obstruct a portion of the socket 210.

With reference to FIG. 7B, slide rail structure 196 includes a rail 216 that is cantilevered from a perimeter of the cover 106. Rail 216 includes an elongate socket 218 and a lip 220. A detent 222 is disposed to obstruct a portion of the socket 218. In the illustrated embodiment, rail structures carried at left and right sides of the shell 102 are minor images, and similar structure carried on one side may be designated for the other side with the same numeral. It should be noted that the terms “rail”, rim”, and “flange” may be used somewhat interchangeably. Any difference in meaning of such terms may be adduced in context.

With reference to FIG. 7C, end capture structure, generally 224, includes a rail 226 that is cantilevered from a perimeter of the cover 106. Rail 226 includes an elongate socket 228 and a lip 230. Lip 230 is formed in harmony with socket structure 232 (see FIG. 8A) carried by top tub 110 to create an interference that resists separation of the joint at that local area and in a direction that is transverse to the axial assembly direction.

Similar to end capture structure 224, end capture structure 234 illustrated generally in FIG. 8B includes a lip 235 that is received in a cooperating socket carried by bottom tub 212. Desirably, a lip, such as lip 212, 220, or 230 is structured in harmony with the socket in which it is received such that an interference is created to resist rotation (about an axis parallel to the joint) of a lip that is seated in its corresponding socket.

FIG. 8C illustrates a double-ended ramp 236 that also is a lip received in an elongate socket 210 in cover 106. When ramp 236 is slid along its cooperating socket 210 substantially to an installed position, it encounters a cooperating detent, such as detent 214. The cooperating detent 214 rides up an approach ramp portion of ramp 236 as tub 112 is displaced in a closing direction, then rides down a retention ramp portion 238 of ramp 236 to a seated position in the area indicated by numeral 238 in FIG. 8C.

As perhaps illustrated best in FIG. 9A, a structural interference created between a retention ramp portion 238 of ramp 236 and its cooperating detent 214 resists undesired displacement of a tub 112 from an installed position with respect to a cover 106. A similar arrangement is illustrated in FIG. 9B, where ramp 240 is structured as a lip that is slidingly disposed in socket 218 (see FIG. 7B) and forms a structural interference in an installed position with detent 222. A plurality of ramps, such as ramp 236, and/or an elongate lip, may be disposed along a side of a cover or tub to interface in engagement within a cooperating socket carried by a corresponding tub or cover.

FIGS. 10A and 10C illustrate how a ramp, or lip, or end capture feature desirably fits in close engagement inside a cooperating socket to resist rotation of the joint about an axis parallel to the joint. Desirably, the interaction between such joint elements resists rotation of the assembled joint, and increases bending strength of an assembled shell 102.

The push-button flex latch 202 illustrated best in FIG. 11 includes a primary engagement surface 242 that forms a structural interference with a perimeter wall of aperture 204 (e.g. see FIG. 5) effective to resist undesired separation between the top tub 110 and the bottom tub 112. A secondary engagement can also be made between structure carried by a cooperating tub and secondary retention socket 244.

It should be noted that a cover 106 is not required to be embodied as a substantially flat plate. Alternative configurations are within contemplation for a cover 106, nonexclusively including placing a parting line at the midpoint of a pair of tub elements. In such case, one of the tub elements may be characterized as a cover, and the other may be characterized as the tub. In similar manner, a socket, ramp, lip, or end capture feature may be carried by either a cover, or a tub element. Further, an overlapping portion of a cantilevered rail or flange may be disposed inside with respect to a cooperating structure on one embodiment, and outside on another.

With reference now to FIG. 11, sometimes it is desirable to include additional provision to resist entry of fluid, and/or dust, into a shell 102 or a resilient layer 150. In certain cases, a covering, such as a transparent membrane 246 or 248, may be affixed to a shell, such as shell 102. In such case, it is preferable for the membrane to be removable and replaceable. A desirable membrane resists entrance of fluid and/or dust, but may permit passage of sound, e.g. for microphone pick-up, or speaker broadcast.

A resilient gasket 250 may be included in certain embodiments to assist in forming a fluid and/or dust resistant seal between a shell and either a layer 150 or device 104. As illustrated, gasket 250 is disposed around a perimeter of display window 128 such that a display window of electronic device 104 directly provides an area effective to resist water entry into shell 102.

In certain embodiments, a shell may be structured in harmony with an energy distributing layer, enclosed electronic device, and one or more membrane associated with one or more window to permit placing the shell into a water-resistant configuration. Aperture(s), access port(s), and window(s) may be covered with suitable water-resistant membrane barrier(s). In such case, water-resistant is distinguished over water-proof. It is recognized that a user can still potentially open an access door to defeat the water-resistant character of desirable embodiments.

FIGS. 13 and 14 illustrate alternative embodiments structured according to certain principles of the invention. The embodiment generally indicated at 260 in FIG. 13 includes a cover 262 and a unitary tub 264. A perimeter edge, generally 266, of tub 264 carries a shelf 268 and a cantilevered rim 270 (see also FIG. 13B). The rim 270 is adapted to overlap cooperating cantilevered flange structure 272, carried by cover 262, at a joint there-between.

Cantilevered flange 272 projects from an inside surface of cover 262 and skirts a portion of the perimeter edge of tub 264. As illustrated, flange 272 is arranged to overlap rim 270 at the joint between cover and tub. Between them, wall elements of flange 272 and rim 270 carry a plurality of cylinder-in-socket retention structures, generally 276. As illustrated in FIGS. 13A and 13B, a cylinder 278 may be carried by rim 270, and a socket 280 is carried by flange 272. The alternative construction is also workable.

Desirably, some sort of connection structure, such as a plurality of cylinder-in-socket structures, of the sort generally indicated at 276, are provided to permit a snap-together connection between tub 264 and cover 262 to form a uni-body enclosure that can be assembled and disassembled a plurality of times without requiring destruction of the retention structures.

The embodiment generally indicated at 290 in FIG. 14 includes additional elements to resist entry of fluid and/or dust into shell 102. Shell gasket 292 is configured to seal the perimeter joint between cover 106 and tub 108. A speaker membrane 294 is disposed to resist entrance of fluid and/or dust through aperture 140. A pair of microphone membranes 296 are disposed to resist entrance of fluid and/or dust through microphone pick-up apertures 132.

A workable material for a hard shell, according to this disclosure, has a minimum flexural modulus of about 200,000 psi. This includes substantially all ABS (250K), Polycarbonate (345K), and ABS Polycarbonate blends, as well as metallic shells. The range for hard shell thickness is typically between about 40 and 100 mils. The inner liner thickness should generally fall within about 10 and 100 mils. Desirably, the combined thickness of the hard shell and energy-distributing liner is typically not more than about 170 mils. A very generalized design rule for preferred embodiments indicates thickness of the hard shell can vary inversely according to a formula including liner thickness, and directly with respect to shell stiffness.

Certain prior art telephone-protection devices include an exterior surface of silicone, which is generally also textured. That sort of surface can have a coefficient of friction greater than 1.0, and make it difficult to slide the device into a pocket. Desirably, a substantial portion of the exterior of an assembly, such as assembly 100, is configured to provide a coefficient of friction of less than about 0.3 to facilitate entry of the assembly 100 into a user's pocket. It is currently believed that a “substantial portion” can encompass about 85%, or more, of the exterior surface.

Preferably, exposed sides of the hard shell 102 are adapted to avoid friction with pocket material by exposing a low-friction material extending for at least about ⅔ total shell length from the bottom end. In this case, “exposed” may be defined to encompass only raised areas adjacent to a recessed insert that fingers could touch, but would not reasonably contact shirt pocket material when sliding a shell 102 into a pocket. For purpose of this disclosure, “low-friction material” may be defined as a material having a coefficient of static friction of less than about 0.3.

One way of estimating the strength of the protective enclosure, or hard shell, is to assume that the cross-section shape is similar to a regular geometric shape such as a rectangle, then apply a three-point bending setup to measure the flexural strength for that shape under load. The formula for such a system is s=3FL/2bd2, where s is flexural strength which is also related to stiffness or rigidity of the outer shell; F is a force applied at the middle of the unsupported span; b is the width of the outer shell; d is the depth or thickness of the outer shell; and where L is the distance between the 2 span supports.

The method of measuring flexural strength is to apply force F until the case integrity starts to fail. That failure can be significant flexing such as is seen with case styles that utilize clip-on hard shells over a soft liner. One such device flexed 20% of d with about 1-2 lbs of pressure. If L=4 in; b=2.5 in; and d=0.5 in, then s=approximately 12-24 psi. Table 1 sets forth actual test results for several commercially available telephone protection cases. As indicated in Table 1, embodiments structured according to certain principles of the invention are projected to carry 50 lbs of force translating to s=approximately 600 psi.

Note that the flexural strength could vary depending on the particular device dimensions, enclosure materials and hard shell wall thickness. A preferred embodiment has a hard shell structured to contain a telephone and to carry a minimum 3-point bending load in excess of about 25 pounds. The bending load is applied with two base points that are spaced apart on one side of the hard shell by 4 inches and the load is applied on the opposite side at the mid-span location.

Also, note that the jarring forces of various impacts can be unpredictable and that this bending test is believed to be the worst case test that certain embodiments of this invention can undergo because tension on the bottom latch is the weakest point. The push-button flex latch 202 is designed to have a double connection including the secondary retention socket 244, and positive camber to at least one connection surface, which will tend to keep the latch engaged during this type of loading. Tests with other orientations are expected to produce many times better results because almost all other impact forces will be with the direction of the connections and tend to reinforce the connection.

An additional advantage of the preferred hard shell construction and rigidity is the number of connection points (which is 11 in the current embodiment but is not limited to 11 and can be many more or even nearly continuous). Note that the latches of the hard shell of a leading commercially available enclosure protrude through the outer cushion layer defeating the ability of the cushion layer to absorb impacts. Preferred embodiments of the invention not only have the advantage of having the cushion layer suspended internally inside the hard shell, but the hard shell uniquely avoids protruding latch or connection points and has somewhat uniform wall thickness. A uniform skin without disruptions is stronger, it may also minimizes impact liabilities as well as potentially slimming the overall enclosure.

TABLE 1 Bending point Model Description (>150 mils) Failure Point APL2-I4SUN-E7- Otter Products Iphone 4/4S Defender 4 lbs (48 psi) 9 lbs (108 psi)- E4OTR_A Series Case -Production case using fasteners failed Polycarbonate material APL4-I4SUN-20- Otter Products Iphone 4/4S 1 lbs (12 psi) 2-3 lbs (24-36 psi)- E4OTR_A Commuter Series Case - Production continued case using polycarbonate material bending SC-RC-4TQ Sharkeye Iphone 4 Protective Case No significant 13 lbs (156 psi) - bending fasteners failed before failure J14 Speck Mighty Vault Case for iPhone 9 lbs (108 psi) 15 lbs (180 psi) - 4/4S continued bending EXO Skullcandy iPhone 4S EXO 11 lbs (132 psi) 17 lbs (204 psi) - Ruggedized Case continued bending MAG450BLK Magpul iPhone 4/4S Executive Field 3 lbs (36 psi 5 lbs (60 psi) - Case continued bending Current Invention - Slide Rail Case - Model using 18 lbs (216 psi) 23 lbs (276) - Preferred Accura 25 SLA material (not fasteners failed Embodiment production worthy) Current Invention - Slide Rail Case - Model using Expected 20- Expected 30- Preferred Machined Polycarbonate material 25 lbs (240- 40 lbs (360- Embodiment (non-production but with production 300 psi) 480 psi) material) Current Invention - Slide Rail Case - Model using Expected 20- Expected 30- Preferred Machined Polycarbonate material 25 lbs (240- 50 lbs (360- Embodiment (non-production but with production 300 psi) 600 psi) material)

While the invention has been described in particular with reference to certain illustrated embodiments, such is not intended to limit the scope of the invention. The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope. 

What is claimed is:
 1. An add-on apparatus to increase ruggedness of a commercially available portable electronic device, the apparatus comprising: a hard shell configured in general agreement with the exterior of said electronic device and comprising enclosing sides including a front side, back side, top side, bottom side, left side, and right side, said sides being arranged to define a first volume, one or more window being disposed in one or more of said sides and configured to permit operation of at least one control of said electronic device when said electronic device is contained inside said shell; and an energy distributing layer structured for disposition inside said shell and defining a second volume in which to receive said electronic device, said energy distributing layer being arranged to space a portion of said electronic device apart from direct contact with said shell.
 2. The apparatus according to claim 1, wherein: said sides are structured and arranged in harmony with said energy distributing layer such that impact energy, generated by dropping said apparatus onto a flat surface, cannot be transferred to an electronic device contained inside said apparatus without first passing through said shell and a portion of said energy distributing layer.
 3. The apparatus according to claim 1, wherein: said shell comprises a plurality of elements that may be assembled to form a uni-body enclosure.
 4. The apparatus according to claim 1, wherein: said shell comprises a tub and a cover; a perimeter edge of said tub comprises a shelf and a cantilevered rim, said rim being adapted to overlap structure of said cover at a joint there-between; a cantilevered flange projects from an inside surface of said cover and skirts a portion of said perimeter edge of said cover, said flange being arranged to overlap said rim at said joint; and wall elements of said flange and said rim carry a plurality of cylinder-in-socket retention structures, said retention structures being configured to effect a snap-together connection between said tub and said cover to form a uni-body enclosure that can be assembled and disassembled a plurality of times without requiring destruction of said retention structures.
 5. The apparatus according to claim 1, wherein: said shell comprises a cover, a top tub, and a bottom tub; a slide rail system is formed in combination between said cover, said top tub, and said bottom tub, said slide rail system being configured to permit slide-assembly of each said tub onto said cover; a push-button flex latch is carried by one said tub and is configured and arranged to removably couple said top tub to said bottom tub when said top tub and said bottom tub are in an assembled location on said cover; and a relief area is formed in said energy distributing element and is arranged to permit a user to impart a transverse deflection to said latch to permit separation of a said tub from said cover.
 6. The apparatus according to claim 5, wherein: a detent-and-ramp structure associated with said slide rail system is configured and arranged to resist sliding a said tub from an installed position.
 7. The apparatus according to claim 1, wherein: said energy distributing layer comprises an elastomeric compound.
 8. The apparatus according to claim 1, wherein: said energy distributing layer comprises memory foam, and a portion of said energy distributing layer is biased in compression upon assembly of said shell.
 9. The apparatus according to claim 1, wherein: said energy distributing layer comprises a two-pocket element, each said pocket being structured to engage a portion of said electronic device in direct contact therein.
 10. The apparatus according to claim 1, wherein: said two-pocket element is structured and arranged to be stretch-fit onto said electronic device during assembly of said apparatus.
 11. The apparatus according to claim 1, wherein: said energy distributing layer comprises a first pocket configured to fit onto the top of said electronic device and a second pocket configured to fit onto the bottom of said electronic device.
 12. The apparatus according to claim 1, wherein: said energy distributing layer comprises a plurality of discrete sections of energy distributing material.
 13. The apparatus according to claim 1, wherein: a portion of said energy distributing layer is affixed to an inside surface of said shell.
 14. The apparatus according to claim 1, wherein: a portion of said energy distributing layer is arranged as a door configured to cooperate with a first window in said shell to permit forming a dust-resistant seal there-between, a hinge of said door permitting rotation of said door in an outward direction through said first window.
 15. The apparatus according to claim 14, further comprising: a membrane disposable to cover a second window in one of said sides.
 16. The apparatus according to claim 15, wherein: said membrane is removable and replaceable.
 17. The apparatus according to claim 1, further comprising: a gasket configured and arranged to form a water-resistant seal, between said shell and said electronic device, around a perimeter of a display window of said shell such that a display window of said electronic device directly provides an area effective to resist water entry into said shell.
 18. The apparatus according to claim 1, wherein: said shell is structured in harmony with said energy distributing layer, said electronic device, and one or more membrane associated with one or more window to permit placing said shell into a fluid-resistant configuration.
 19. The apparatus according to claim 1, wherein: said shell is structured to contain a telephone and to carry a minimum 3-point load in excess of about 25 pounds, wherein: two base points are spaced apart on one side of said shell by 4 inches and the load is applied on the opposite side at the mid-span location.
 20. An apparatus, comprising: a hard shell arranged to define a first volume, one or more window being disposed in said shell and configured to permit operation of at least one control of an electronic device when said electronic device is contained inside said shell; an energy distributing layer structured for disposition inside said shell and defining a second volume in which to receive said electronic device, said energy distributing layer being arranged to space said electronic device apart from direct contact with said shell; and a portion of said energy distributing layer being arranged as a door configured to cooperate with a first window in said shell to permit forming a dust-resistant seal there-between, a hinge of said door permitting rotation of said door in an outward direction through said first window. 